CDMA/TDD mobile communication system and method

ABSTRACT

Control section  125  at base station  100  in a CDMA/TDD mobile communication system assigns one or more fixed forward link time slots to a plurality of time slots divided at a communication frame at a predetermined interval, and forward link time slots and reverse link time slots to the time slots except for the fixed forward link time slots by allocating corresponding to a ratio of a total information volume of a forward link to a total information volume of a reverse link in the system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slots, and to transmit forward link and reverse link traffic channel signals using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a CDMA/TDD mobile communication systemand method applying a same band transmission/reception system forassigning time slots at the same radio frequency band to communicateover a reverse link and a forward link alternately.

2. Description of the Invention

Conventionally, as a mobile communication system using a CDMA (CodeDivision Multiple Access) system, a W-CDMA (Wideband CDMA) system usinga DS (Direct Sequence) system is known. The W-CDMA system uses a FDD(Frequency Division Duplex) system as a duplex system.

As a duplex system, a TDD (Time Division Duplex) system is known otherthan the FDD. The TDD system uses a same band transmission/receptionsystem for assigning time slots at the same radio frequency band tocommunicate a reverse link and a forward link alternately, which is alsocalled Ping-Pong system.

In addition, a multiple access system is a line connection system overwhich a plurality of stations concurrently communicate at the samefrequency band. The CDMA system employs a technique for performing amultiple access by a spread spectrum communication in which informationsignals are spread by a spreading code to transmit over a spread band.In the DS system, information signals are multiplied by a spreading codein spreading.

In the DS-CDMA system, since a plurality of communication links sharethe same frequency band, there is a problem to control eachcommunication wave level at a reception to be equal (near-far problem).In other words, the conquest over this problem is necessary to achievethe CDMA communication system.

The near-far problem is severer at a reception of a base station forconcurrently receiving radio signals transmitted from a plurality ofmobile stations (mobile radio terminal devices) each locating at adifferent place. Therefore, it is mandatory at the mobile stationpropagation path condition.

In the TDD system, propagation path conditions such as fading correlatewhen intervals of forward and reverse links are short enough because thesame frequency band is used for the forward and reverse links. It isthereby possible to perform a transmission power control by open-loopcontrol.

Some of such CDMA mobile communication system comprises a TDDconfiguration for dividing a communication frame into a plurality oftime slots to assign each of traffic channel and control channel to atime slot to communicate over a plurality of links.

FIG. 1 illustrates a frame diagram in a conventional CDMA/TDD mobilecommunication system.

FIG. 1 illustrates an example where one frame 1 is divided into eighttime slots 0 to 7, time slots 0 to are assigned to a forward link andtime slots 4 to 7 are assigned to a reverse link.

In forward link 2 toward a mobile station (not shown) from a basestation (not shown), common control channel 3 such as synchronizationcontrol channel, a dedicated control channel and user informationchannel 4 that are transmitted between the base station and a dedicatedmobile station are multiplexed. In reverse link 5 toward the basestation from the mobile station, the dedicated control channel and userinformation channel 6 are multiplexed.

The mobile station starts receiving when it is turned on, and acquiressynchronization with the base station by detecting the synchronizationcontrol channel of common control channel 3 in forward link 2. Then themobile station performs a line connection via the dedicated controlchannel to start communicating with user information channel 4. At thispoint, the mobile station measures reception quality of an assignedforward link time slot, and based on the measurement result, performs atransmission power control of an assigned reverse link time slot.

However, in the conventional CDMA/TDD mobile communication systemdescribed above, when an assignment of time slots to forward link andreverse link is changed corresponding to information volume of theforward and reverse links, a configuration of the synchronizationcontrol channel becomes irregular. It thereby takes a longer time for amobile station to acquire synchronization with a base station when it isturned on.

In addition, in each communication link, since an interval of theassigned forward link time slot and the assigned reverse link time slotis long, the propagation path conditions of the forward and reverselinks do not correlate so much, thereby decreasing an effect of anopen-loop controlled transmission power control.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a CDMA/TDD mobilecommunication system and method for enabling a synchronizationacquisition time with a base station at a mobile station to beshortened, and enabling open-loop controlled transmission power controlto function effectively when an assignment of time slots to forward andreverse links is changed corresponding to an information volume in thecase where the information volumes of the forward and reverse links areasymmetry.

The object is achieved by a CDMA/TDD mobile communication systemcomprising a base station apparatus having a control section forassigning one or more fixed forward link time slots to a plurality oftime slots divided at a communication frame at a predetermined interval,while assigning forward link time slots and reverse link time slots tothe time slots except for the fixed forward link time slots byallocating the time slots corresponding to a ratio of a totalinformation volume of a forward link Lo a total information volume of areverse link in the system, in order to transmit a control channelsignal including a synchronization control channel signal using thefixed forward link time slots, and to transmit a traffic channel signalof the forward link and a traffic channel signal of the reverse linkrespectively using the forward link time slots and the reverse link timeslots that are allocated according to the number of time slotsrespectively required corresponding to the respective informationvolume.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a frame diagram applied in a conventional CDMA/TDD mobilecommunication system;

FIG. 2 is block diagram of a base station in a CDMA/TDD mobilecommunication system according to a first embodiment of the presentinvention;

FIG. 3 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in the CDMA/TDD mobile communication systemaccording to the first embodiment of the present invention;

FIG. 4 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a DMA/TDD mobile communication systemaccording to a second embodiment of the present invention;

FIG. 5 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to a third embodiment of the present invention;

FIG. 6 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to a fourth embodiment of the present invention;

FIG. 7 is a block diagram of a mobile station in a CDMA/TDD mobilecommunication system according to a fifth embodiment of the presentinvention;

FIG. 8 is an integration result diagram obtained by the mobile stationaccording to the fifth embodiment integrating correlation value of areceived signal with a spreading code of a forward synchronizationcontrol channel at each sampling timing over four time slots intervalstarting from an arbitrary time.

FIG. 9 is a frame diagram Illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to a sixth embodiment of the present invention; and

FIG. 10 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to a seventh embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A CDMA/TDD mobile communication system and method according to theembodiments of the present invention are specifically explained belowwith reference to attached drawings.

(First Embodiment)

FIG. 2 is block diagram of a base station in a CDMA/TDD mobilecommunication system according to the first embodiment of the presentinvention.

Base station 100 illustrated in FIG. 2 is composed of coding section 104having first coding section 101, second coding section 102 and thirdcoding section 103, spreading section 108 having first spreading section105, second spreading section 106 and third spreading section 107,multiplexing section 109, D/A conversion section 110, transmissionfrequency conversion section 111, reception frequency conversion section112, A/D conversion section 113, allocating section 114, correlationdetection section 118 having first correlation detection section 115,second correlation detection section 116, and third correlationdetection section 117, decoding section 122 having first decodingsection 119, second decoding section 120 and third decoding section 121,transmission/reception antenna 123, transmission/reception switchingsection 124 and control section 125.

Coding sections 101 to 103 execute coding of first to third forward linkdedicated control channel signals 131, 132 and 133 respectively.Spreading sections 105 to 107 executed spreading the coded channelsignals 134, 135 and 136 respectively.

Multiplexing section 109 multiplexes the spread channel signals 137 to139. D/A conversion section 110 converts the multiplexed signal 140 intoanalogue signal 141. Transmission frequency conversion section 111converts the analogue signal 141 into transmission signal 142 with radiofrequency.

Transmission/reception switching section 124 switchestransmission/reception antenna 123 for a transmission site and atransmission site to connect. The transmission signal 142 is transmittedfrom transmission/reception antenna through transmission/receptionswitching section 124 to a mobile station (not shown).

The reception frequency conversion section 112 converts received signal431 with radio frequency into signal 144 with baseband frequency. Thereceived signal 431 is received at transmission/reception antenna 123and transmitted through transmission/reception switching section 124 tothe section 112.

A/D conversion section 113 converts the signal 144 with base bandfrequency into digital received signal 145.

Allocating section 114 allocates digital received signal 145 to channelsignals 146, 147 and 148.

Correlation detection sections 115 to 117 detect correlation of reverselink common dedicated channel signals 146 to 148 respectively. Decodingsections 119 to 121 decode correlation detection channel signals 149,150 and 151 to output channel decoded signals 152, 153 and 154. Controlsection 125 controls over each section described above.

In a configuration described above, forward link common channel (such assynchronization control channel) signals 131 to 133 are coded andconstructed into frames at coding sections 101 to 103 and output tospreading sections 105 to 107 respectively. The coding may be an errorcorrection coding, and in this case, interleaving processing is alsoexecuted.

Spreading sections 105 to 107 respectively spread coded channel signals134 to 136 with a spreading code to output spread signals 137 to 139 tomultiplexing section 109. The spreading code may be assigned fromcontrol section 125.

Multiplexing section 109 provides spread signals 137 to 139 at timeslots to multiplex according to an instruction from control section 125.At this stage, channel signals provided at the same time slot aremultiplexed. In the case where the multiplexing processing is executed,a transmission power control may be performed to control an amplitude ofeach of channel spread signals 137 to 139.

Digital multiplexed signal 140 is converted into analogue signal 141 inD/A conversion section 110. The analogue signal 141 is converted intotransmission signal 142 with radio frequency in transmission frequencyconversion section 111. The transmission signal 142 is transmitted fromtransmission/reception antenna 123 through transmission/receptionswitching section 124.

At this stage, transmission/reception switching section 124 connectstransmission/reception antenna 123 to transmission frequency conversionsection 111 for a forward link time slot and to reception frequencyconversion section 112 for a reverse link time slot according to aninstruction from control section 125.

On the other hand, reception signal 143, which is received attransmission/reception antenna 123 from a mobile station, is input toreception frequency conversion section 112 throughtransmission/reception switching section 124. Reception frequencyconversion section 112 converts the received signal 143 with radiofrequency into signal 144 with baseband frequency.

A/D conversion section 113 converts the analogue signal 144 withbaseband frequency into digital signal 145 to output to allocatingsection 114. Allocating section 114 divides the digital signal 145 intoreverse common control channel signals 146 to 148 according to aninstruction of control section 125 to output to correlation detectionsections 115 to 117 respectively.

Correlation detection sections 115 to 117 despread the reverse commoncontrol channel signals 146 to 148 to detect correlation of a receivedsignal with a spreading code. Each spreading code may be instructed bycontrol section 125.

Detected correlation values (correlation signals) 149 to 151 arerespectively output to decoding sections 119 to 121, which decodereverse common control channel signals based on correlation values 149to 151. At this stage, when a mobile station executes an errorcorrection coding for a reverse link, an error correction decoding withdeinterleaving processing is executed.

In addition, each common section may be provided to use for all channelsaccording to time slots instead of using coding sections 101 to 103,spreading sections 105 to 107, correlation detection sections 115 to117, and decoding sections 119 to 121.

An assignment control of time slots is explained from among controlsexecuted by control section 125 with reference to FIG. 3. FIG. 3 is aframe diagram illustrating an assignment of time slots at acommunication frame in a CDMA/TDD mobile communication system. Theassignment illustrates an example where one frame 201 is divided into 16time slots 0 to 15.

In FIG. 3, 202 indicates a time slot at which a forward link commoncontrol channel signal and a forward link user information channelsignal are provided, 203 indicates a time slot at which only a forwardlink user information channel signal is provided, and 204 indicates atime slot at which a reverse link channel signal is provided.

Control section 125 first compares an information volume of the forwardlink with that of reverse link and determines the numbers of time slotsto be assigned to the forward link and the reverse link. At this point,the number of time slots necessary to transmit a forward link commoncontrol channel signal including a synchronization control channelsignal is primarily assigned to the forward link. The other time slotsare assigned to the forward link and reverse link taking the informationvolumes into consideration.

Then, the forward link common control channel signal including thesynchronization control channel signal is provided at a time slot at apredetermined time slots interval at a frame, accordingly the time slotis assigned for a forward link time slot.

Further, the rest of forward link time slots are provided at the frame.At this point, the forward link time slots are provided primarily attime slots except for those following just after the forward link timeslots to transmit control channel signals including synchronizationcontrol channel signals. Then the other time slots are assigned for thereverse link time slots.

In the forward link time slots at which forward link common controlchannel signals including synchronization control channel signals areprovided, the forward link common control channel signals may be notonly provided, but also other forward link channel signals may beprovided. In this case, a plurality of channel signals provided in thetime slot are multiplexed to transmit.

FIG. 3 illustrates examples of assigning sixteen time slots at a frame.

(A) in FIG. 3 illustrates the case where four time slots 0, 4, 8 and 12are assigned for forward link time slots, and the other twelve timeslots are assigned for reverse link time slots.

(B) in FIG. 3 illustrates the case where eight time slots are assignedfor forward link time slots, and the other eight time slots are assignedfor reverse link time slots. The times slots 0, 4, 8 and 12 are assignedfor forward link time slots to transmit forward link common controlchannel signals including synchronization control channel signals andthe time slots 2, 6, 10 and 14 are further assigned for forward linktime slots. The time slots 1, 3, 5, 7, 9, 11, 13 and 15 are assigned forreverse link time slots.

(C) in FIG. 3 illustrates the case where twelve time slots are assignedfor forward link time slots, and the other four time slots are assignedfor reverse link time slots. The time slots 0, 4, 8 and 12 are assignedfor forward link time slots to transmit forward link common controlchannel signals including synchronization control channel signals andthe time slots 2, 3, 6, 7, 10, 11, 14 and 15 are further assigned forforward link time slots. The time slots 1, 5, 9, and 13 are assigned forreverse link time slots.

(D) in FIG. 3 illustrates the case where fifteen time slots are assignedfor forward link time slots, and the other one time slot is assigned fora reverse link time slot. The time slots 0, 4, 8 and 12 are assigned forthe forward link time slots to transmit forward link common controlchannel signals including synchronization control channel signals andthe time slots 2, 3, 5, 6, 7, 9, 10, 11, 13, 14 and 15 are furtherassigned for forward link time slots. The time slot 1 is assigned forthe reverse link time slot.

In (c) and (D) in FIG. 3, the reverse link time slots are positionedjust after the time slots assigned for forward link time slots totransmit common control channel signals including synchronizationcontrol channel signals. As a result, in the case where a closed-loopcontrol is performed in the system, it is possible for a mobile stationto control transmission power using a TPC bit contained in the controlchannel signal in the received forward link common control channelsignal. Accordingly, the mobile station can respond rapidly to apropagation environment such as fading.

The assignment of time slots may be changed manually corresponding to achange of an information volume, or changed automatically according tothe change of the information volume caused by a new connection or abreak, or at predetermined intervals.

A mobile station acquires synchronization with a base station when it isturned on by first despreading a received signal with a spreading codeused in the synchronization control channel signal to detect thesynchronization control channel signal.

Under such condition, the mobile station does not know an assignment oftime slots for a forward link and a reverse link when it is turned on,however knows in advance that a synchronization control channel signalis positioned once every four slots with three time slots inserted.Therefore, the mobile station can detect a timing of the synchronizationcontrol channel signal by integrating correlation values over every fourtime slots interval.

The mobile station decodes the common control channel signal includingthe synchronization control channel signal using the detected timing inorder to recognize positions of forward link time slots and reverse linktime slots and time slots assigned to each channel.

Then the mobile station performs connection processing using therecognized common control channel and dedicated control channel toestablish a user information channel. Signals of user informationchannel between a mobile station and a base station are provideddifferently for a forward link and a reverse link at a frame 201.Therefore, the time difference between a forward link user informationchannel time slot and a reverse link user information channel time slotis sometimes large with the other many time slots inserted between thosetime slots.

In the case of performing a reverse link transmission power controlusing an open-loop control, since the correlation characteristic ofpropagation path conditions of a forward link and a reverse link isused, the large time difference introduces the low correlationcharacteristic, resulting in a reduced accuracy of the transmissionpower control.

However, since the forward link common control channel signal istransmitted every four time slots, when a reception quality is measuredusing the forward link common control channel signal and thetransmission power control is performed based on the measured receptionquality, the time difference between the forward link time slot used tomeasure the reception quality and the reverse link time slot to betransmitted under the transmission power control are a two time slotstime at maximum, thereby enabling an efficient transmission powercontrol.

In addition, It is preferable to use the arbitrary number of time slotscomposing a frame other than sixteen. It is also preferable to provide aforward link common control channel signal every arbitrary number oftime slots other than every four time slots. It is further preferable toprovide a forward link common control channel signal at a predeterminedperiodical pattern other than at equal intervals.

As described above, according to the first embodiment, under the controlof control section 125 in base station 100, some of time slots at acommunication frame are assigned primarily to fixed forward link timeslots at predetermined intervals and the other time slots are allocatedto forward link time slots and reverse link time slots corresponding toa ratio of the total information volume of the reverse link to that ofthe forward link in a system, in order to transmit a control channelsignal including a synchronization control channel signal using thefixed forward link time slot and transmit traffic channel signals offorward link and reverse link respectively using the forward link timeslots and the reverse link time slots that are allocated according tothe number of time slots respectively required corresponding to therespective information volume. The above processing makes it possible toshorten a time for a mobile station to acquire synchronization with abase station even when an assignment of time slots for forward andreverse links is changed corresponding to the information volumes offorward link and reverse link in the case where the information volumesare asymmetry, thereby enabling an open-loop controlled transmissionpower control to function effectively.

(Second Embodiment)

FIG. 4 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to the second embodiment of the present invention.

FIG. 4 illustrates an example where one frame 301 is divided intosixteen time slots 0 to 15. In FIG. 4, the reference number 302indicates a time slot at which a forward link common control channelsignal and a forward link user information channel signal are provided,the reference number 303 indicate a time slot at which only a forwardlink user information channel signal is provided, and the referencenumber 304 indicate a time slot at which a reverse link channel signalis provided.

Control section 125 of base station 100 illustrated in FIG. 2 firstcompares an information volume of the forward link with that of reverselink and determines the numbers of time slots to be assigned to theforward link and the reverse link.

At this point, the number of time slots necessary to transmit a forwardlink common control channel signal including a synchronization controlchannel signal is primarily assigned to the forward link. The other timeslots are assigned to the forward link and reverse link taking theinformation volumes into consideration.

Then, the forward link common control channel signal including thesynchronization control channel signal is provided at a slot every twoslots with a slot inserted, accordingly the time slot is assigned for aforward link time slot. Further, the other forward link time slots areprovided at the frame, and the rest of the time slots are assigned forreverse link time slots.

In the forward link time slots at which forward link common controlchannel signals including synchronization control channel signals areprovided, the forward link common control channel signals includingsynchronization control channel signals may be not only provided, butalso other forward link channel signals may be provided. In this case, aplurality of channel signals provided in the same time slot aremultiplexed to transmit.

(A) in FIG. 4 illustrates the case where eight time slots are assignedfor forward link time slots, and the other eight time slots are assignedfor reverse link time slots. The time slots 0, 2, 4, 6, 8, 10, 12 and 14are assigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals, and the time slots 1, 3, 5, 7, 9, 11, 13 and 15 are assignedfor reverse link time slots.

(B) in FIG. 4 illustrates the case where twelve time slots are assignedfor forward link time slots, and the other eight time slots are assignedfor reverse link time slots. The time slots 0, 2, 4, 6, 8, 10, 12 and 14are assigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 1, 5, 9 and 13 are further assigned forforward link time slots. The time slots 3, 7, 11, and 15 are assignedfor reverse link time slots.

(C) in FIG. 4 illustrates the case where fourteen time slots areassigned for forward link time slots, and the other two time slots areassigned for reverse link time slots. The time slots 0, 2, 4, 6, 8, 10,12 and 14 are assigned for forward link time slots to transmit forwardlink common control channel signals including synchronization controlchannel signals and the time slots 1, 3, 5, 9, 11 and 13 are furtherassigned for forward link time slots. The time slots 7 and 15 areassigned for reverse link time slots.

(D) in FIG. 3 illustrates the case where fifteen time slots are assignedfor forward link time slots, and the other one slot is assigned for areverse link time slot. The time slots 0, 2, 4, 6, 8, 10, 12 and 14 areassigned for forward link time slots to transmit forward link commoncontrol channel signals including synchronization control channelsignals and the time slots 1, 3, 5, 7, 9, 11 and 13 are further assignedfor forward link time slots. The time slot 15 is assigned for a reverselink time slot.

As describe above, in FIG. 4, time slots provided just after time slotsto transmit forward link common control channel signals includingsynchronization control channel signals are always reverse link timeslots.

In other words, by providing one of time slots to transmit forward linkcommon control channel signals including synchronization control channelsignals every two time slots, i.e., with one other time slot insertedbetween those, even when reverse time slots are provided in any timeslots, it is configured that the time slots just before the reverse linktime slots are always the forward link time slots to transmit commoncontrol channel signals including synchronization control channelsignals.

Therefore, in the case where a closed-loop control is performed in thesystem, it is possible for a mobile station to control transmissionpower using a TPC bit contained in the control channel signal in thereceived forward link common control channel signal. Accordingly, themobile station can respond rapidly to a propagation environment such asfading.

The assignment of time slots may be changed manually corresponding to achange of an information volume, or changed automatically according tothe change of the information volume caused by a new connection or abreak, or at predetermined intervals.

Under such condition, a mobile station (not shown) acquiressynchronization with a base station when it is turned on by firstdespreading a received signal with a spreading code used in thesynchronization control channel signal to detect the synchronizationcontrol channel signal.

The mobile station does not know an assignment of time slots for aforward link and a reverse link when it is turned on, however the mobilestation can detect a timing of the synchronization control channelsignal by integrating correlation values over every two time slotsinterval.

Then, the mobile station decodes the common control channel signalincluding the synchronization control channel signal using the detectedtiming in order to recognize positions of forward link time slots andreverse link time slots and time slots assigned to each channel, andperforms connection processing using the recognized common controlchannel and dedicated control channel to establish a user informationchannel.

Use information channel slots between a mobile station and a basestation are positioned differently for forward link and reverse link ata frame. Therefore, the time difference between a forward link userinformation channel time slot and a reverse link user informationchannel time slot is sometimes large with the other many time slotsinserted between those time slots.

In the case of performing a reverse link transmission power controlusing an open-loop control, the large time difference introduces the lowcorrelation characteristic of propagation path conditions of the forwardlink and reverse link, resulting in a reduced accuracy of thetransmission power control. However, since the common control channel istransmitted once every two slots, when the transmission power control isperformed based on the reception quality obtained by using the receivedcommon control channel, it is possible to use the reception quality ofthe forward link time slot just before the reverse link time slot to betransmitted under the transmission power control, thereby enabling aneffective transmission power control. In addition, it is also preferableto use the arbitrary number of time slots composing a frame other thansixteen.

As described above, according to the second embodiment, a time slot inevery two slots is assigned for a fixed forward link time slot and theother time slots are allocated for forward link time slots and reverselink time slots corresponding to a ratio of the total information volumeof forward link to that of the reverse link in a system, in order totransmit a control channel signal including a synchronization controlchannel signal using the fixed forward link time slot and transmittraffic channel signals of forward link and reverse link respectivelyusing the forward link time slots and the reverse link time slots thatare allocated according to the number of time slots respectivelyrequired corresponding to the respective information volume. The aboveprocessing makes it possible to shorten a time for a mobile station toacquire synchronization with a base station even when an assignment oftime slots for forward and reverse links is changed corresponding to theinformation volumes of forward link and reverse link when theinformation volumes are asymmetry, thereby enabling an open-loopcontrolled transmission power control to function effectively.

(Third Embodiment)

FIG. 5 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to the third embodiment of the present invention.

FIG. 5 illustrates an example where one frame 401 is divided intosixteen time slots 0 to 15. In FIG. 5, the reference number 402indicates a time slot at which a forward link common control channelsignal and a forward link user information channel signal are provided,the reference number 403 indicates a time slot at which a forward linkuser information channel signal is provided, and the reference number404 indicates a time slot at which a reverse link channel signal isprovided.

Control section 125 of base station 100 illustrated in FIG. 2 firstcompares an information volume of the forward link with that of reverselink and determines the numbers of time slots to be assigned to theforward link and the reverse link.

At this point, the number of time slots necessary to transmit a forwardlink common control channel signal including a synchronization controlchannel signal is primarily assigned to the forward link. The other timeslots are assigned to the forward link and reverse link taking theinformation volumes into consideration.

Then, the forward link common control channel signal including thesynchronization control channel signal is provided at a slot every eighttime slots with seven time slots inserted, accordingly the time slot isassigned for a forward link time slot. Further, the other forward linktime slots are provided at the frame, and the rest of time slots areassigned for reverse link time slots.

In the forward link time slots at which forward link common controlchannel signals including synchronization control channel signals areprovided, the forward link common control channel signals includingsynchronization control channel signals may be not only provided, butalso other forward link channel signals may be provided. In this case, aplurality of channel signals provided in the same time slot aremultiplexed to transmit.

(A) in FIG. 5 illustrates the case where two time slots are assigned forforward link time slots, and the other fourteen time slots are assignedfor reverse link time slots. The time slots 0 and 8 are assigned forforward link time slots to transmit forward link common control channelsignals including synchronization control channel signals. The othertime slots 1 to 7 and 9 to 15 are assigned for reverse link time slots.

(B) in FIG. 5 illustrates the case where eight time slots are assignedfor forward link time slots, and the other eight time slots are assignedfor reverse link time slots. The time slots 0 and 8 are assigned forforward link time slots to transmit forward link common control channelsignals including synchronization control channel signals and the timeslots 2, 4, 6, 10, 12 and 14 are further assigned for forward link timeslots. The time slots 1, 3, 5, 7, 9, 11, 13 and 15 are assigned forreverse link time slots.

(C) in FIG. 5 illustrates the case where twelve time slots are assignedfor forward link time slots, and the other four time slots are assignedfor reverse link time slots. The time slots 0 and 8 are assigned forforward link time slots to transmit forward link common control channelsignals including synchronization control channel signals and the timeslots 2, 3, 4, 6, 7, 10, 11, 12, 14 and 15 are further assigned forforward link time slots. The time slots 1, 5, 9 and 13 are assigned forreverse link time slots.

(D) in FIG. 5 illustrates the case where fifteen time slots are assignedfor forward link time slots, and the other one time slot is assigned fora reverse link time slot. The time slots 0 and 8 are assigned forforward link time slots to transmit forward common control channelsignals including synchronization control channel signals and the timeslots 2 to 7 and 9 to 15 are further assigned for forward link timeslots. The other time slot 15 is assigned for a reverse link time slot.

As describe above, in FIG. 5, time slots provided just after time slotsto transmit forward link common control channel signals includingsynchronization control channel signals are always reverse link timeslots.

In other words, by providing one of time slots to transmit forward linkcommon control channel signals including synchronization control channelsignals every eight time slots, i.e., with seven other time slotsinserted between those, even though reverse time slots are provided atany time slots, it is configured hat the time slot just before at leastone of the reverse link time slots at a frame is always a forward linktime slot to transmit common control channel signals includingsynchronization control channel signals.

Therefore, in the case where a closed-loop control is performed in thesystem, it is possible for a mobile station to control transmissionpower using a TPC bit contained in the control channel signal in thereceived forward link common control channel signal. Accordingly, themobile station can respond rapidly to a propagation environment such asfading.

The assignment of time slots may be changed manually corresponding to achange of an information volume, or changed automatically according tothe change of the information volume caused by a new connection or abreak, or at predetermined intervals.

Under such condition, a mobile station (not shown) acquiressynchronization with a base station when it is turned on by firstdespreading a received signal with a spreading code used in thesynchronization control channel signal to detect the synchronizationcontrol channel signal.

The mobile station does not know an assignment of time slots for aforward link and a reverse link when it is turned on, however the mobilestation can detect a timing of the synchronization control channelsignal by integrating correlation values over every eight time slotsintervals.

Then, the mobile station decodes the common control channel signalincluding the synchronization control channel signal using the detectedtiming in order to recognize positions of forward link time slots andreverse link time slots and time slots assigned to each channel, andperforms connection processing using the recognized common controlchannel and dedicated control channel to establish a user informationchannel.

User information channel slots between a mobile station and a basestation are positioned differently for forward link and reverse link ata frame. Therefore, the time difference between a forward link userinformation channel time slot and a reverse link user informationchannel time slot is sometimes large with the other many time slotsinserted between those time slots.

In the case of performing a reverse link transmission power controlusing an open-loop control, the large time difference introduces the lowcorrelation characteristic of propagation path conditions of the forwardlink and reverse link, resulting in a reduced accuracy of thetransmission power control. However, since the common control channel istransmitted once every eight slots, when the transmission power controlis performed based on the reception quality obtained by using thereceived common control channel, it is possible to use the receptionquality of the forward link time slot just before the reverse link timeslot to be transmitted under the transmission power control, therebyenabling an effective transmission power control. In addition, it isalso preferable to use the arbitrary number of time slots composing aframe other than sixteen.

As described above, according to the third embodiment, a time slot inevery eight slots is assigned for a fixed forward link time slot and theother time slots are allocated for forward link time slots and reverselink time slots corresponding to a ratio of the total information volumeof reverse link to that of the forward link in a system, in order totransmit a control channel signal including a synchronization controlchannel signal using the fixed forward link time slot and transmittraffic channel signals of forward link and reverse link respectivelyusing the forward link time slots and the reverse link time slots thatare allocated according to the number of time slots respectivelyrequired corresponding to the respective information volume. The aboveprocessing makes it possible to shorten a time for a mobile station toacquire synchronization with a base station even when an assignment oftime slots for forward and reverse links is changed corresponding to theinformation volumes of forward link and reverse link in the case wherethe information volumes are asymmetry, thereby enabling an open-loopcontrolled transmission power control to function effectively. In thiscase, it is possible to obtain many variations of allocationconfiguration of the number of forward link time slots and the number ofreverse link time slots.

(Fourth Embodiment)

FIG. 6 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to the fourth embodiment of the present invention.

FIG. 6 illustrates an example where one frame 501 is divided intosixteen time slots 0 to 15. In FIG. 6, the reference number 502indicates a time slot at which a forward link common control channelsignal and a forward link user information channel signal are provided,the reference number 503 indicates a time slot at which a forward linkuser information channel signal is provided, and the reference number504 indicates a time slot at which a reverse link channel signal isprovided.

Control section 125 of base station 100 illustrated in FIG. 2 firstcompares an information volume of the forward link with that of reverselink and determines the numbers of time slots to be assigned to theforward link and the reverse link.

At this point, the number of time slots necessary to transmit a forwardlink common control channel signal including a synchronization controlchannel signal is primarily assigned to the forward link. The other timeslots are assigned to the forward link and reverse link taking theinformation volumes into consideration.

Then, the forward link common control channel signal including thesynchronization control channel signal is provided at a slot in everysixteen slots, accordingly the time slot is assigned for a forward linktime slot. Further, the other forward link time slots are provided atthe frame, and the rest of time slots are assigned for reverse link timeslots.

In the forward link time slots at which forward link common controlchannel signals including synchronization control channel signals areprovided, the forward link common control channel signals includingsynchronization control channel signals may be not only provided, butalso other forward link channel signals may be provided. In this case, aplurality of channel signals provided in the time slot are multiplexedto transmit.

(A) in FIG. 6 illustrates the case where one time slot is assigned for aforward link time slot, and the other fifteen time slots are assignedfor reverse link time slots. The time slot 0 is assigned for a forwardlink time slot to transmit forward link common control channel signalsincluding synchronization control channel signals. The other time slots1 to 15 are assigned for reverse link time slots.

(B) in FIG. 4 illustrates the case where eight time slots are assignedfor forward link time slots, and the other eight time slots are assignedfor reverse link time slots. The time slot 0 is assigned for a forwardlink time slot to transmit forward link common control channel signalsincluding synchronization control channel signals and the time slots 2,4, 6, 8, 10, 12 and 14 are further assigned for forward link time slots.The time slots 1, 3, 5, 7, 9, 11, 13 and 15 are assigned for reverselink time slots.

(C) in FIG. 6 illustrates the case where twelve time slots are assignedfor forward link time slots, and the other four time slots are assignedfor reverse link time slots. The time slot 0 is assigned for a forwardlink time slot to transmit common control channel signals includingsynchronization control channel signals and the time slots 2, 3, 4, 6,7, 8, 10, 11, 12, 14 and 15 are further assigned for forward link timeslots. The time slots 1, 5, 9 and 13 are assigned for reverse link timeslots.

(D) in FIG. 3 illustrates the case where fifteen time slots are assignedfor forward link time slots, and the other one time slot is assigned forreverse link time slots. The time slot 0 is assigned for a forward linktime slot to transmit common control channel signals includingsynchronization control channel signals and the time slots 2 to 15 arefurther assigned for forward link time slots. The time slot 1 isassigned for a reverse link time slot.

As describe above, in FIG. 6, time slots provided just after time slotsto transmit forward link common control channel signals includingsynchronization control channel signals are always reverse link timeslots.

In other words, by providing one of time slots to transmit forward linkcommon control channel signals including synchronization control channelsignals every sixteen time slots, i.e., with fifteen other time slotsinserted between those, even though reverse time slots are provided inany time slots, it is configured that the time slot just before at leastone of the reverse link time slots at a frame is always a forward linktime slot to transmit common control channel signals includingsynchronization control channel signals.

Therefore, in the case where a closed-loop control is performed in thesystem, it is possible for a mobile station to control transmissionpower using a TPC bit contained in the control channel signal in thereceived forward link common control channel signal. Accordingly, themobile station can respond rapidly to a propagation environment such asfading.

The assignment of time slots may be changed manually corresponding to achange of an information volume, or changed automatically according tothe change of the information volume caused by a new connection or abreak, or at predetermined intervals.

Under such condition, a mobile station (not shown) acquiressynchronization with a base station when it is turned on by firstdespreading a received signal with a spreading code used in thesynchronization control channel signal to deject the synchronizationcontrol channel signal.

The mobile station does not know an assignment of time slots for aforward link and a reverse link when it is turned on, however the mobilestation can detect a timing of the synchronization control channelsignal by integrating correlation values over every fifteen time slotsintervals.

Then, the mobile station decodes the common control channel signalincluding the synchronization control channel signal using the detectedtiming in order to recognize positions of forward link time slots andreverse link time slots and time slots assigned to each channel, andperforms connection processing using the recognized common controlchannel and dedicated control channel to establish a user informationchannel.

User information channel slots between a mobile station and a basestation are positioned differently for forward link and reverse link ata frame. Therefore, the time difference between a forward link userinformation channel time slot and a reverse link user informationchannel time slot is sometimes large with the other many time slotsinserted between those time slots.

In the case of performing a reverse link transmission power controlusing an open-loop control, the large time difference introduces the lowcorrelation characteristic of propagation path conditions of the forwardlink and reverse link, resulting in a reduced accuracy of thetransmission power control. However, since the common control channel istransmitted once every sixteen slots, when the transmission powercontrol is performed based on the reception quality obtained by usingthe received common control channel, it is possible to use the receptionquality of the forward link time slot just before the reverse link timeslot to be transmitted under the transmission power control, therebyenabling an effective transmission power control. In addition, it isalso preferable to use the arbitrary number of time slots composing aframe other than sixteen.

As described above, according to the fifth embodiment, a time slot inevery sixteen slots is assigned for a fixed forward link time slot andthe other time slots are allocated for forward link time slots andreverse link time slots corresponding to a ratio of the totalinformation volume of reverse link to that of the forward link in asystem, in order to transmit a control channel signal including asynchronization control channel signal using the fixed forward link timeslot and transmit traffic channel signals of forward link and reverselink respectively using the forward link time slots and the reverse linktime slots that are allocated according to the number of time slotsrespectively required corresponding to the respective informationvolume. The above processing makes it possible to shorten a time for amobile station to acquire synchronization with a base station even whenan assignment of time slots for forward and reverse links is changedcorresponding to the information volumes of forward link and reverselink in the case where the information volumes are asymmetry, therebyenabling an open-loop controlled transmission power control to functioneffectively. In this case, it is possible to obtain many variations ofallocation configuration of the number of forward link time slots andthe number of reverse link time slots.

(Fifth Embodiment)

FIG. 7 is block diagram of a mobile station as an example ofcommunication terminal devices in a CDMA/TDD mobile communication systemaccording to the fifth embodiment of the present invention.

Mobile station 600 illustrated in FIG. 7 is composed of coding section601, spreading section 602, amplifying section 603, D/A conversionsection 640, transmission frequency conversion section 605, receptionfrequency conversion section 606, A/D conversion section 607, allocatingsection 608, correlation detection section 611 including firstcorrelation detection section 609, and second correlation detectionsection 610, decoding section 614 including first decoding section 612and second decoding section 613, transmission/reception antenna 615,transmission/reception switching section 616 and control section 617.

Coding section 601 codes reverse link channel signal 621. Spreadingsection 602 spreads coded signal 622. Amplifying section 603 amplifiesspread signal 623.

D/A conversion section 604 converts digital amplified signal 624 intoanalogue signal 625. Transmission frequency conversion section 605converts the analogue signal 625 into transmission signal 626 with radiofrequency.

Transmission/reception switching section 616 switchestransmission/reception antenna 615 for a transmission site and atransmission site to connect. The transmission signal 626 is transmittedfrom transmission/reception antenna 615 through transmission/receptionswitching section 616 to a base station illustrated in FIG. 2 by radiocommunication.

Reception frequency conversion section 606 converts received signal 627with radio frequency into signal 628 with baseband frequency. Thereceived signal 627 is received at transmission/reception antenna 615and transmitted through transmission/reception switching section 616 tothe section 606.

A/D conversion section 607 converts the signal 628 with basebandfrequency into digital received signal 629. Allocating section 608allocates the digital received signal 629 to channel signals 630 and631.

Correlation detection sections 609 and 610 detect respectively forwardlink common dedicated channel signals 630 and 631. Decoding sections 612and 613 decode channel correlation detection signals 632 and 633 tooutput channel decoded signals 634 and 635 respectively. Control section617 controls over each section described above.

In a configuration described above, reverse link channel signal 612 iscoded and constructed into frames at coding section 602 and output tospreading section 602. The coding may be an error correction coding, andin this case, interleaving processing is also executed.

Spreading section 602 spreads coded signal 622 with a spreading code andoutputs spread signal 623 to amplifying section 603. The spreading codemay be assigned from control section 617.

Amplifying section 603 provides the spread signal 623 at a time slotassigned according to an instruction from control section 617 andperforms transmission power control by amplifying or decreasing anamplitude of the spread signal 623 according to an instruction fromcontrol section 617 to output to D/A conversion section 604.

D/A conversion section 604 converts digital amplified 624 into analoguesignal 625 to output to transmission frequency conversion section 605.Transmission frequency conversion section 605 converts the analoguesignal 625 into transmission signal 626 with radio frequency to outputto transmission/reception switching section 616.

Transmission/reception switching section 616 connectstransmission/reception antenna 615 to transmission frequency conversionsection 605 for a reverse link time slot and to reception frequencyconversion section 606 for a forward link time slot according to aninstruction from control section 617.

In other words, with respect to reverse link time slots, transmissionsignal 626, which is subjected to the conversion of frequency into theradio frequency at reception frequency conversion section 605, istransmitted from transmission/reception antenna 123 to a base station100.

On the other hand, with respect to forward link time slots, receivedsignal 627 that is received at transmission/reception antenna 123 isinput to reception frequency conversion section 606.

Reception frequency conversion section 606 converts the received signal627 with radio frequency into received signal 628 with basebandfrequency to output to A/D conversion section 607. A/D conversionsection 607 converts the analogue signal 628 into digital signal 629 tooutput to allocating section 608.

Allocating section 608 divides digital signal 629 into signals 630 and631 according to an instruction from control section 617 to output tocorrelation detection sections 609 and 610 respectively.

Correlation detection sections 609 and 610 despread divided signals 630and 631 respectively to detect correlation of a received signal with aspreading code and obtain correlation values 632 and 633 respectively.Each spreading code may be instructed from control section 125. Detectedcorrelation values 632 and 633 are respectively output to decodingsections 612 and 613, while output to control section 617.

Decoding sections 612 and 613 decode forward common control channelsignals 634 and 635 using correlation values 632 and 633. At this point,when base station 100 executes an error correction coding for a forwardlink, an error correction decoding with deinterleaving processing isexecuted.

In addition, each common section may be provided to use for all channelsaccording to time slots instead of using correlation detection sections609 and 610, and decoding sections 612 and 613.

The following description will explain a manner how a mobile stationacquires synchronization with a base station when it is turned on withreference to the case illustrated in FIG. 2 where a time slot totransmit a forward link common control channel signal including asynchronization control channel signal is provided once every four timeslots with three other time slots inserted.

When mobile station 600 is turned on, it does not know an assignment andtiming of time slots for reverse link and forward link because it doesnot acquire synchronization with a base station yet.

Then mobile station 600, as illustrated in FIG. 8, integrates acorrelation value of a received signal with a spreading code of forwardlink synchronization control channel at each sample timing within a fourtime slots length 701 starting from an arbitrary time t1 and repeats theintegration at four time slots intervals.

When the number of integration times is increased, since noise componentis reduced, it is detected that an integration value of correlationvalue at sampling timing 702 illustrated in FIG. 8 that conforms to atiming of the synchronization control channel signal becomes larger thanthat at other sampling timing.

However, as the number of integration times is too increased, a samplingtiming by mobile station 600 shifts from the target timing becausemobile station 600 does not acquire synchronization with the basestation yet. Therefore too large number of integration times makes itdifficult to detect timing 702 for synchronization control channelsignal.

When common control channel signals including synchronization controlchannel signals are not provided at certain intervals, it is difficultto reduce the noise component by the integration described above, makingit difficult to detect a timing of synchronization control channelsignal.

However, when common control channel signals including synchronizationcontrol channel signals are provided at certain intervals even thoughthe numbers of time slots assigned for reverse link and forward link arevaried, it is possible to execute integration at the certain intervals,thus facilitating a detection of the timing of synchronization controlchannel signal.

In a configuration of mobile station 600 illustrated in FIG. 7, suchsynchronization acquisition by integration is executed in controlsection 617, however a synchronization section (not shown) may beprovided besides control section 617.

As described above, according to the fifth embodiment, a mobile stationdetects a synchronization control channel signal by integratingcorrelation values of a received signal with a spreading code atpredetermined time slots intervals, thereby making it possible toacquire synchronization with a base station easily with less time evenwhen an assignment of time slots for forward and reverse links ischanged corresponding to an information volume in the case where theinformation volumes of forward and reverse links are asymmetry.

(Sixth Embodiment)

FIG. 9 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to the sixth embodiment of the present invention.

FIG. 9 illustrates an example where one frame 801 is divided intosixteen time slots 0 to 15. In FIG. 9, 802 indicates a time slot atwhich a forward link common control channel signal is provided, 803indicates a time slot at which a forward link user information channelsignal is provided, and 804 indicates a time slot at which a reverselink user information channel signal is provided.

In other words, one frame 801 is divided into sixteen time slots so asto provide forward link common control channel signals includingsynchronization control signals at the eight time slots 0, 2, 4, 6, 8,10, 12 and 14, forward link user information channel signals at the timeslots 1, 5, 9 and 13, and reverse link user information channel signalsat the time slots 3 and 11.

The transmission power control operation of control section 617 inmobile station 600 illustrated in FIG. 7 is explained with reference toFIG. 9.

Since the forward link user information channel is an dedicated channelbetween a mobile station 600 and a base station, the transmission poweris controlled so that reception quality at mobile station 600 meets apredetermined requirement.

On the other hand, since forward link common control channel is a commonchannel, the transmission power control is not performed based on arequirement of reception quality at mobile station 600. As a result, thereception quality sometimes deteriorates temporarily due to fading.

In the case of performing a transmission power control for reverse linkunder open-loop control, the similarity of propagation paths of reverselink and forward link is used. In this case, when a time intervalbetween a forward link time slot to measure a reception quality and arevere link time slot to transmit, the similarity of propagation pathconditions of reverse link and forward link becomes low, resulting in areduction of accuracy of the transmission power control.

The high reception quality introduces a more accurate estimation ofpropagation path conditions, however the propagation path conditionchanges as an interval between reception and transmission is increased.

Taking the above problems into consideration, a propagation pathcondition is estimated by combining a reception quality at each timeslot with an appropriate weight. In the case where the propagation pathcondition changes rapidly, a weight for a common control channel signalat the time slot 2 just before the time slot 3 to be transmitted is sethigh and weights for a common control channel signal or user informationchannel signal at the other time slots are set low. It may be performedthat the weight for the common control channel signal at the time slot 2is set at 1 and the weights for a common control channel signal or userinformation channel signal at the other time slots are set at 0.

On the other hand, in the case where the propagation path conditionchanges slowly, since it is possible to estimate the propagation pathcondition with a high accuracy, a weight for a user information channelsignal at the time slot 1 is set high and weights for common controlchannel signals at the time slots 0 and 2 are set low. It may beperformed that the weight for the user information channel signal at thetime slot 1 is set at 1 and weights for common control channel signalsat time slots 0 and 2 are set at 0.

In addition, the above case describes about the transmission powercontrol of the reverse link user information channel signal at the timeslot 3, however the same processing is performed to the transmissionpower control of the reverse link user information channel signal at thetime slot 11.

The above case further describes about the example where three timeslots just before the time slot to be transmitted are used to combinewith weights, however it is also preferable to use forward link channelsignals at time slots before the three time slots.

In this case, the above example corresponds to the case where weightsfor channel signals at time slots four time slots before the time slotto be transmitted are set at 0. In addition, the above case describesthat forward user information channel signals are provided at forwardlink time slots except for forward link time slots at which commoncontrol channel signals are provided, however the same processing isperformed in another case where forward link user information channelsignals and forward link common control channel signals are provided atthe same time slots.

Further, user information channel signals may be provided only atforward link time slots without being provided at reverse link timeslots. This case corresponds to weights for user information channelsignals being set at 0.

In addition, a propagation path condition is estimated by combiningsignals with weights in the above case, however it is also preferable topredict a propagation path condition via which a time slot will betransmitted using a time transition of the estimated propagation pathcondition to control transmission power.

Further, in the above case, the transmission power control is performedonly under the open-loop control.

However, the same processing is performed in the transmission powercontrol under the combination of closed-loop control where a basestation instructs transmission power to a mobile station via a forwardlink.

As described above, according to the sixth embodiment, a mobile stationdetects a synchronization control channel signal by integratingcorrelation values of a received signal with a spreading code atpredetermined time slots intervals, thereby making it possible toacquire synchronization with a base station easily with less time evenwhen an assignment of time slots for forward and reverse links ischanged corresponding to an information volume in the case where theinformation volumes of forward and reverse links are asymmetry.

Further, the mobile station measures a reception quality of a forwardlink common control channel signal provided at a time slot just before atime slot of a reverse link user information channel signal even thoughthe reverse link user information channel signal is provided at anyreverse link time slot, thereby enabling an effective open-loopcontrolled transmission power control even when a propagation pathcondition changes rapidly.

(Seventh Embodiment)

FIG. 10 is a frame diagram illustrating an assignment of time slots at acommunication frame applied in a CDMA/TDD mobile communication systemaccording to the seventh embodiment of the present invention.

FIG. 10 illustrates an example where one frame 901 is divided intosixteen time slots 0 to 15. In FIG. 10, 902 indicates a time slot atwhich a forward link common control channel signal is provided, 903indicates a time slot at which a forward link user information channelsignal is provided, and 904 indicates a time slot at which a reverselink user information channel signal is provided.

In other words, one frame 901 is divided into sixteen time slots so asto provide forward link common control channel signals includingsynchronization control signals at the eight time slots 0, 2, 4, 6, 8,10, 12 and 14, forward link user information channel signals at the timeslots 5 and 10, and reverse link user information channel signals at thetime slots 3 and 11.

The transmission power control operation of control section 617 inmobile station 600 illustrated in FIG. 7 is explained with reference toFIG. 10. In addition, the explanation will describe the case where aweight for forward link channel signal provided at a time slot justbefore a time slot to be transmitted is 1 and weights for the otherforward link channel signals are 0.

A common control channel signal is provided at the time slot 2 justbefore the time slot 3 to be transmitted. Accordingly, the transmissionpower control is performed based on a reception quality of the forwardlink common control channel signal at the time slot 2.

On the other hand, both common control channel signal and userinformation channel signal are provided at the time slot 10 just beforethe time slot 11 to be transmitted. Accordingly, it is possible toperform the transmission power control based on both reception qualitiesof the forward link common control channel signal and user informationchannel signal.

Two correction detection sections are necessary to measure bothreception qualities of the forward link common control channel signaland user information channel signal. However, a single correlationdetection section is enough by providing a configuration where bothreception qualities can be switched to measure.

In a configuration where a reception quality of the forward link commoncontrol channel signal is measured, the transmission power control isperformed based on the reception quality of the forward link commoncontrol channel signal that has a lower accuracy, not depending on thetime slot assignment of user information channel signal for forward andreverse links, even when a forward link user information channel signalis provided at a slot just before a slot at which a reverse link userinformation channel signal is provided.

Therefore, an effect of transmission power control is decreased.However, by providing a configuration where a channel to measure areception quality is switched to a user information channel when aforward link user information channel signal is provided at a slot justbefore a slot at which a reverse link user information channel signal isprovided, it is possible to measure the reception quality of the userinformation channel signal measurable with a high accuracy, therebyenabling an effective transmission power control of the reverse linkuser information channel signal.

As described above, according to the seventh embodiment, a mobilestation detects a synchronization control channel signal by integratingcorrelation values of a received signal with a spreading code atpredetermined time slots intervals, thereby making it possible toacquire synchronization with a base station easily with less time evenwhen an assignment of time slots for forward and reverse links ischanged corresponding to an information volume in the case where theinformation volumes of forward and reverse links are asymmetry.

Further, the mobile station switches a reception quality of a forwardlink common control channel signal and that of a forward link userinformation signal provided at a time slot just before a time slot of areverse link user information channel signal even though the reverselink user information channel signal is provided at any reverse linktime slot, thereby enabling an effective open-loop controlledtransmission power control even when a propagation path conditionchanges rapidly.

As been obvious from the above-mentioned explanation, according to thepresent invention, it is possible for a mobile station to reduce aacquisition time of synchronization with a base station even when anassignment of time slots for forward and reverse links is changedcorresponding to an information volume in the case where the informationvolumes of forward and reverse links are asymmetry, thereby enabling theopen-loop controlled transmission power control to function effectively.

What is claimed is:
 1. A base station apparatus in a CDMA/TDDcommunication system that employs a communication frame divided into aplurality of time slots, each of which is assigned one of a forward linkand a reverse link of the communication system, the base stationapparatus comprising: an assignor that assigns a forward link commoncontrol channel to position fixed time slots disposed at regularintervals among the plurality of time slots; and a controller thatassigns a forward link user information channel and a reverse link userinformation channel to time slots, other than the position fixed timeslots, in accordance with a ratio of an information volume on theforward link and an information volume on the reverse link.
 2. The basestation apparatus of claim 1, the forward link common control channelcomprising a synchronization control channel.
 3. The base stationapparatus of claim 1, wherein the position fixed time slots are disposedat regular intervals of every second time slot.
 4. The base stationapparatus of claim 1, wherein the position fixed time slots are disposedat regular intervals of every fourth time slot.